The association between cognitive reserve and cognitive trajectories among older adults in Europe

Abstract

AbstractBackgroundThe literature on cognitive reserve (CR) and cognitive trajectories is limited in in the using of individual CR measures rather than composite CR measure. Moreover, to date, the findings about the association between CR and cognitive trajectories are conflicting and inconsistent.AimsTo examine the longitudinal association of a composite CR measure and each individual indicator of CR on cognitive decline, both combined and on individual domains, over 6‐years follow up, adjusting for age, gender, number of chronic diseases, functional disability and physical activityMethodsWe conducted a longitudinal analysis using a cohort study on 55,340 participants from 16 European countries, aged 50 and more taken from the survey of health, Aging, and Retirement in Europe (SHARE). We used cognitive performance assessments (including immediate memory, delayed memory, verbal fluency and numeracy) and information on CR factors (encompassing education, occupation and cognitive activities) collected in four waves conducted at 2‐years interval from 2011 to 2017. First, structural equation modeling was used to construct the composite CR score, and then was analyzed by tertile. Finally, linear mixed‐effect models were used to examine the study aims.ResultsAt baseline, compared with highest CR, middle and lowest CR showed large differences in combined cognition and in all individual domains. At the longitudinal results revealed that compared with the highest CR, the lowest CR was related to a faster decline in composite cognition score over time, despite the small difference, it remains significant (β: ‐0.02, 95% confidence interval [CI]: ‐0.03 to ‐0.01), as well as in all specific cognitive domains. However, no association was found for the middle CR trajectory. Among the individual CR measures, education was associated with better cognitive performance over time (β: 0.01, 95%CI: 0.01 to 0.01) and occupation complexity was associated with less decline over time (β: ‐0.01, 95%CI: ‐0.01 to ‐0.00), but cognitive activities were not associated with cognition.ConclusionsThe composite CR provides a comprehensive measure in preserve cognitive functions and in avoiding cognition decline, more than using individual CR indicator.